单项选择题

Vaccines for viral diseases are often produced from ______.

A．plant cells
B．human hormones
C．crop plants
D．bacteria
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单项选择题
According to the passage, if you were camping in 10℃ weather and the temperature dropped to 10℃ below zero, you could compensate for this by______.
A．sleeping in a tent with special layers of clothing
B．sleeping in a tent on the side of a hill
C．sleeping on the side of a hill
D．sleeping on the side of a hill out of the wind
单项选择题
What will be one effect of the new biotechnology on plants
A．They will grow anywhere in the world.
B．Some will be able to grow in salty soils.
C．They will become poisonous to pests.
D．Using nitrogen from the air they will be able to cress fertilize.
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